1. Field of the Invention
The present invention relates to a process for the alkylation of organic aromatic compounds. More particularly the invention relates to a process for the concurrent alkylation and distillation of reaction components (reactants and products) in a catalyst bed wherein the catalyst is slurried in the organic aromatic compound and passed through a reaction distillation zone to contact olefin feed. The reaction distillation zone comprises inert distillation packing contained within the lower portion of a distillation column reactor.
2. Related Art
Ethyl benzene and cumene are currently produced by the reaction of benzene and the respective olefin, i.e., ethylene and propylene by acid catalysis. In some known processes the catalyst is highly corrosive and has a relatively short life, e.g., AlCl.sub.3, H.sub.3 PO.sub.4 on clay, BF.sub.3 on alumina, and others require periodic regeneration, e.g., molecular sieves. The exothermicity of the reaction and the tendency to produce polysubstituted benzene require low benzene conversions per pass with large volume recycle in conventional processes.
U.S. Pat. Nos. 4,371,714 and 4,469,908 disclose straight pass alkylation of aromatic compounds using molecular sieve catalysts in fixed beds, however, both references disclose coking of the catalyst as a problem which necessitates frequent unit shut down and regeneration of the catalyst. U.S. Pat. Nos. 4,316,997 and 4,423,254 both disclose the use of acidic resins in fixed beds for the alkylation of aromatic compounds. Coking is also a problem with these catalysts.
Recently a new method of carrying out catalytic reactions has been developed, wherein the components of the reaction system are concurrently separable by distillation, using the catalyst structures as the distillation structures. Such systems are described variously in U.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,250,052; 4,302,356; 4,307,254; and 4,443,559 commonly assigned herewith. Briefly, a structure described there is a cloth belt with a plurality of pockets spaced along the belt, which is then wound in a helix about a spacing material such as stainless steel knitted mesh. These units are then disposed in the distillation column reactor.
In commonly owned, copending U.S. patent application Ser. No. 122,485 filed 11/15/87, the process of alkylating aromatic compounds with olefins was carried out in a catalytic distillation system using a catalyst structure as described above, using either molecular sieves or acidic resins as particle packing in the pockets. This process has a far greater resistance to coking than the straight pass systems.
The present system differs from catalytic distillation, because the catalyst bed is not fixed and does not serve as the distillation structure in the system. Hence the present system is designated as Reactive Distillation.TM..
Advantages of the present invention are that the catalysts are not highly corrosive and do not require periodic cyclic regeneration, the heat of reaction is used efficiently, only low volume of recycle is required and the feed ratios can approach unity.